Roofing underlayment with nail sealing system

ABSTRACT

A sheet of roofing underlayment comprises a base layer, a water-impermeable coating layer laminated to one side of the base layer, and a plurality of spaced-apart sealant areas between the coating layer and the base layer, comprising a sealant adapted to form a seal around a fastener penetrating the sheet. The sealant area may be continuous or intermittent strips. The sealant forms a water-tight seal around the fasteners used to attach the roofing underlayment to a roof deck.

FIELD OF THE INVENTION

The invention pertains to roofing underlayments, and in particular to a system for preventing water leakage around fasteners that are used to secure roofing underlayment to a roof deck.

BACKGROUND OF THE INVENTION

The basic structure of a typical roofing underlayment is a woven scrim layer (or a non-woven layer) with a waterproof coating on both sides. In use, nails are driven through the roofing underlayment to attach it to a roof deck. This makes holes through the underlayment and there is a susceptibility to water leakage around the nails. It is known in the art to include in a multilayer roofing underlayment a layer that is adapted to seal around nails, e.g. Thai et al., US 2010/0178827; Binkley et al., US 2007/0077838; Zickell et al., US 2007/0071946; and Sandrasegaran et al., WO 2010/070466. However, these systems require use of a full layer of the sealant, including across areas of the sheet where nailing will not occur.

SUMMARY OF THE INVENTION

The invention provides nailing sealant areas or strips inside the layers of a sheet of underlayment that provide a seal around the fasteners passing through the sheet.

According to one aspect of the invention, there is provided a sheet of roofing underlayment, comprising a base layer, a water-impermeable coating layer laminated to a first side of the base layer, and a plurality of spaced-apart sealant areas between the coating layer and the base layer, comprising a sealant adapted to form a seal around a fastener penetrating the sheet.

Further aspects of the invention and features of specific embodiments of the invention are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view through one embodiment of the roofing underlayment.

FIG. 2 is a cross-sectional view through the underlayment of FIG. 1 nailed to a roof deck.

FIG. 3 is a cross-sectional view through a second embodiment of the underlayment.

FIG. 4 is a cross-sectional view through a third embodiment of the underlayment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 2, the roofing underlayment 10 comprises a base layer, namely a woven scrim layer 12, laminated to a first coating layer 14 on one side and to a second coating layer 16 on the opposite side.

The scrim comprises woven tapes which may be made of various resins, including polyolefins such as polyethylene and polypropylene, polyesters, polystyrene, nylon, and ethylene acrylic copolymers. The base layer may be a woven, non-woven or film layer. The coating layers are water impermeable and may comprise any of the same resins as the scrim. The scrim may have a weight of about 75 grams per square meter, alternatively a weight in the range of 25-150 gsm. The coatings may have a thickness of about 1.5 mil, alternatively a thickness in the range of 0.3-3.5 mil.

The sealant areas 18 are spaced-apart strips positioned between the scrim 12 and the first coating layer 14, which in use is the upper layer of the sheet. In the view of FIG. 1, the strips 18 extend into the plane of the paper. The sealant material may be any of various seal-forming adhesives, including hot melt adhesive, silicone, glue, modified bitumen and rubberized asphalt. The sealant areas 18 may be black or dark-colored to be visible through the coating 14. During the manufacture of the underlayment, the strips of sealant are applied between the first coating layer 14 and the scrim layer 12. They are placed in nailing areas such as along the longitudinal edges of the sheet, and, alternatively also across the middle of the sheet. For example, there may be three continuous parallel strips of sealant 18 across the sheet (at the middle and two longitudinal edges) of about 2 inches (5 cm) wide and about 5 mil thick. Alternatively, the strips may be intermittent rather than continuous, or a combination of continuous and intermittent.

In one embodiment, a sealant is employed that does not cure during the process of manufacturing the roofing underlayment. It remains liquid until a fastener, e.g. a nail, passes through the coating, exposing the sealant to air or humidity and causing the sealant to cure and form a rubbery gasket around the nail. In a second embodiment, the sealant cures during the process of manufacturing the roofing underlayment. The thickness of the top coating layer 14 or of the scrim layer 12, or both, may be reduced in the area of the sealant strips 18, as shown in FIG. 1, so that the sheet 10 has a substantially uniform thickness. This facilitates winding up of the sheet evenly into a roll, avoiding build-up in the roll in the areas of the strips. Alternatively, roll buildup can be managed by making the strips intermittent, or having intermittent spots of sealant. Alternatively, roll buildup can be managed by osculation of the sealant strips. In such embodiment, the osculation of the strips is done by means of the mechanism of delivering the stops being slightly moved left and right traversing across the web, preventing the sealant strips from stacking upon themselves layer after layer. Instead of the roll containing build-up in one spot the build-up is distributed over a space of approximately 8 inches (20 cm).

FIG. 2 shows the sheet of roofing underlayment 10 laid in place on a roof deck 22, with the second coating layer 16 being the bottom layer in direct contact with the deck, and the first coating layer 14 being the upper layer. Nails 20 are driven through the sheet along the strips 18, forming holes 24 through the sheet. The sealant forms a seal around the nails, preventing water infiltration to the deck. Alternatively, staples or screws can be used in place of nails.

Referring next to FIG. 3, a further embodiment of the roofing underlayment 30 has additional sealant areas. Sealant areas or strips 32 are provided on the underside of the sheet, laminated to the outside of the second coating layer 16, aligned with the sealant areas 18 between the first coating layer 14 and the scrim layer 12. Additional sealant areas or strips 34 are provided on the upper side of the sheet, laminated to the first coating layer 14 and aligned with the sealant areas 18 and 32. This arrangement enhances the sealing around fasteners driven through the sealing areas 34, 18, 32. Alternatively, the roofing underlayment 30 may have only the internal sealant areas 18 and the top sealant areas 34, or only the internal sealant areas 18 and the bottom sealant areas 32.

FIG. 4 shows a further embodiment of the roofing underlayment 40. The sealant area 18 is positioned between the scrim layer 12 and the second coating layer 16 (in use, the layer in contact with the roof deck), rather than between the scrim layer 12 and the first coating layer 14 (in use, the top layer). The roofing underlayment 40 is otherwise the same as the roofing underlayment 10 as described above.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the following claims. 

1. A sheet of roofing underlayment, comprising: (a) a base layer; (b) a water-impermeable coating layer laminated to a first side of the base layer; and (c) a plurality of spaced-apart sealant areas between the coating layer and the base layer, comprising a sealant adapted to form a seal around a fastener penetrating the sheet.
 2. A sheet according to claim 1, wherein the sealant is uncured and is adapted to cure upon exposure to air or humidity.
 3. A sheet according to claim 1, wherein the sealant is cured.
 4. A sheet according to claim 1, wherein the sealant is one of a hot melt adhesive, silicone, glue, modified bitumen and rubberized asphalt.
 5. A sheet according to claim 1, wherein the sealant areas are colored and visible through the coating.
 6. A sheet according claim 1, wherein the sealant areas comprise continuous or intermittent strips.
 7. A sheet according to claim 6, wherein the strips are located along two longitudinal edges of the sheet.
 8. A sheet according to claim 7, wherein at least one continuous or intermittent strip is located along a middle part of the sheet.
 9. A sheet according to claim 1, wherein the base layer is a scrim.
 10. A sheet according to claim 1, wherein the base layer is a non-woven.
 11. A sheet according to claim 1, wherein the base layer is a film.
 12. A sheet according to claim 1, wherein the base layer comprises one of a polyolefin, a polyester, polystyrene, nylon, and an ethylene acrylic copolymer.
 13. A sheet according to claim 1, wherein the coating layer comprises one of a polyolefin, a polyester, polystyrene, nylon, and an ethylene acrylic copolymer.
 14. A sheet according to claim 1, further comprising a second coating layer laminated to a second side of the base layer.
 15. A sheet according to claim 1, wherein the thickness of the base layer or the coating layer, or both, adjacent to the sealant areas is less than the thickness of the base layer or the coating layer, respectively, in non-adjacent areas.
 16. A sheet according to claim 15, wherein the sheet has a substantially uniform thickness.
 17. A sheet according to claim 6, wherein the strips osculate along a longitudinal direction of the sheet.
 18. A sheet according to claim 1, further comprising a second plurality of spaced-apart sealant areas laminated to the outside of the sheet and aligned with the sealant areas between the coating layer and the base layer.
 19. A sheet of roofing underlayment, comprising: (a) a base layer; (b) a first water-impermeable coating layer laminated to a first side of the base layer; (c) a second water-impermeable coating layer laminated to a second side of the base layer; and (d) a first plurality of spaced-apart sealant areas between the coating layer and the base layer, comprising a sealant adapted to form a seal around a fastener penetrating the sheet.
 20. A sheet according to claim 19, further comprising a second plurality of spaced-apart sealant areas laminated to the outside of the first coating layer and aligned with the first plurality of sealant areas.
 21. A sheet according to claim 19, further comprising a third plurality of spaced-apart sealant areas laminated to the outside of the second coating layer and aligned with the first plurality of sealant areas. 